#1999 7.3 INJECTOR DRIVER MODULE TESTING DRIVER#
The computer determines this based on engine load and driver demand by monitoring various sensors. The computer controls how long the injector solenoid is energized (pulse-width, or time on in milliseconds), but it also determines the pressure of the fuel being injected by controlling the pressure of the oil (IPR duty-cycle, or the percentage of time on vs. As long as the poppet valve is open and oil is flowing into the injector, fuel will be injected. When fuel pressure inside the injector reaches approximatly 2700 psi, it causes the injector pintle to rise off its seat and fuel is injected into the cylinder from the nozzel. The intensifier piston is forced down, pressurizing the fuel inside the injector. When the injector solenoid is actuated, it opens a poppet valve which allows high pressure oil to flow into the intensifier piston. The IDM sends a 110 volt pulse-width modulated signal to the injector solenoid. As the computer determines that a cylinder should fire it signals the Injector Driver Module. Also supplied to the injectors is high pressure engine oil. Fuel is supplied to the injectors through fuel rails inside the cylinder heads. What has been done on the PowerStroke is both of these systems are used in conjuntion with each other. But a diesel engine uses heat from compression to ignite the air fuel mixture, and this high compression requires high injection pressures. Since gasoline engines have an ignition system to ignite the air/fuel mixture in the cylinders, fuel pressure only needs to be sufficient to supply the injectors and provide an adequate spray pattern to ensure efficient combustion. Gasoline engines with electronic injection use a pressurized fuel system and the computer varies the actuation of the injector based on input from various sensors in order to control the amount of fuel to the cylinders. Also, the amount of fuel injected is dependent on the mechanical operation of the injection pump governor, which adjusts volume based on engine load/RPM. The drawback to this system is that any air which enters the fuel lines will affect the operation of the injectors, or even prevent them from operating. Older diesels used a hydraulic injection system in which fuel pressurized by the injection pump would actuate the injector.
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Understanding how the injectors work on the PowerStroke engine can help in diagnosing a concern with this engine. How the PowerStroke injection system works